Server capacity issue

lukin

I am working for a small IT company and we have two virtual servers (Windows Server 2008) with SQL databases on them. I am a bit of a novice when it comes to server capacity so I would like to know how many databases each can take before it gets overloaded.
Each db is connected to a hosted site located on IIS on the server (I don't know if there is a limit on how many sites a server can host; I think it is more the databases I should be concerned about?)

The first server has:

• 4 GB RAM
• AMD OPTERON 2.10 GHZ processor
• SQL Server 2008
• 100 databases (some are not used). The DB's in total size are 9 GB. They have been in existence for about a year.
• 70 sites on IIS.
• 10 GB free of 100 GB hard drive (this is rather worrying but I think this is because there is no recycle bin present; I will have to resolve this).

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The second server has:

• 8 GB RAM
• AMD OPTERON 2.20 GHZ processor.
• SQL SERVER 2008 R2
• 70 databases (some are not used).The DB's in total size are 7 GB); one is one GB, 4 others are 0.5 GB each.
• 40 sites on IIS
• 25 GB free of 100 GB

I'm probably giving a bit too much information there but just a rough idea from someone who knows about these issues would be appreciated. Thanks.

yeppydeppy

If they are virtual servers it will depend on the capacity of the hardware - is there any spare disk space? Can you add in additional space from a SAN? As for the databases, I don't know much about SQL except that it like to use a lot of disk space and there is a way to compact and delete these. Either ask a SQL DBA or get some training in it.

seamus

The issue isn't so much the number of databases and sites, but how busy each of them are. You could have 2000 databases on a server, but if each database only handles 100 transactions a day, then you wouldn't need much power behind it.

Pretty much the same for the websites. Processing power and RAM does come into play for IIS as you're probably hosting sites running ASP/C#/PHP/etc, all of which have an overhead in processing power.

For example, one of our servers hosts a single 560GB database. It has 48GB of RAM, and it needs every bit of it.
So the "limit" of any server is entirely dependent on the needs of the applications in question.

I'm sure there are standard calculations you can make for determining how much minimum RAM & processing power you need per site & database, and from that you can calculate an upper limit on your sites & databases. At a high level any database server will make exceptionally heavy use of RAM and so plugging in more RAM will help. Database servers also tend to thrash the crap out of your disks, but without knowing how the disks are configured on the virtual host I can't really give any advice there.
Really what you need to begin doing is setting up performance counters and logs and analysing the system usage - you're looking for bottlenecks and such, and also to find out what sites and databases are the biggest consumers of resources.

For what you're doing with so many sites and databases, what you really need to be looking at is a per-site configuration which puts each application into its own walled garden so it can't consume all of the resources on the server. This will also allow you to calculate an in-house upper limit on the number of sites/DBs per server and allow you plan your resources effectively.

lukin

Thanks for the replies, I need to have some way of monitoring the performance on a continuing basis as the number of databases increases over time and likewise with the reads and writes to those dbs.
I could write a performance analysis to a log and have it automatically emailed to me every day.
There's no point checking performnce now and then because if a problem arises it may be too late.